Add device policy to disallow shutdown - ash UI modifications

ash/system/tray/default_system_tray_delegate.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/system/tray/default_system_tray_delegate.h"
 
 #include <string>
 
 #include "ash/session/session_state_delegate.h"
 #include "ash/shell.h"
@@ skipping 251 matching lines @@
 }
 
 void DefaultSystemTrayDelegate::AddCustodianInfoTrayObserver(
     CustodianInfoTrayObserver* observer) {
 }
 
 void DefaultSystemTrayDelegate::RemoveCustodianInfoTrayObserver(
     CustodianInfoTrayObserver* observer) {
 }
 
+void DefaultSystemTrayDelegate::AddShutdownPolicyObserver(
+    ShutdownPolicyObserver* observer) {
+}
+
+void DefaultSystemTrayDelegate::RemoveShutdownPolicyObserver(
+    ShutdownPolicyObserver* observer) {
+}
+
+void DefaultSystemTrayDelegate::ShouldRebootOnShutdown(
+    const RebootOnShutdownCallback& callback) {
+}
+
 }  // namespace ash